| Journal: | Revista brasileira de geofisica |
| Database: | PERIÓDICA |
| System number: | 000338458 |
| ISSN: | 0102-261X |
| Authors: | Oliveira-Junior., Josibel Gomes de1 Medeiros, Walter Eugenio de1 |
| Institutions: | 1Universidade Federal do Rio Grande do Norte, Centro de Ciencias Exatas e da Terra, Natal, Rio Grande do Norte. Brasil |
| Year: | 2008 |
| Season: | Oct-Dic |
| Volumen: | 26 |
| Number: | 4 |
| Pages: | 437-449 |
| Country: | Brasil |
| Language: | Portugués |
| Document type: | Artículo |
| Approach: | Analítico, descriptivo |
| English abstract | Laboratory and field experiments were carried out in order to investigate the causes of GPR reflections inside non-consolidated sand samples. In the sand samples, the content of water, heavy minerals grain size were varied and the velocity of propagation of GPR pulses were measured using antennas of 400 MHz and 900 MHz. In a laboratory experiment, it was verified the increase of the dielectric constant due to the increase in water content. Wyllie & Gregory (1953) and Topp et al. (1980) models furnish good previsions of experimental data, specially the first one when it is considered the entire data set (two frequencies). However, it was verified that the velocity estimates are systematically greater for the higher frequency (900 MHz), a fact which is not predicted by both models. For dry sand samples, it was verified a relatively minor increase of the dielectric constant with the increase in heavy minerals. Also for dry sand samples, no dependence of the dielectric constant was observed with grain size variation. On the other hand, for a field in situ experiment, where samples of sand were taken to perform grain size characterization, it was verified that the grain size might has an indirect influence on the dielectric constant because it may control water adsorption |
| Portuguese abstract | Experimentos em laboratorio e campo foram realizados com o objetivo de investigar as causas das reflexoes de pulsos de GPR em corpos arenosos nao consolidados. As amostras dos corpos foram preparadas variando-se o conte´udo de agua, granulometria e minerais pesados. Utilizando antenas de 400 MHz e 900 MHz foram feitas medidas do tempo duplo de propagacao nas amostras. Para medidas de laborat´orio, verificou-se um aumento na constante dieletrica a medida que o conteudo de ´agua cresceu. Os modelos de Wyllie & Gregory (1953) e de Topp et al. (1980) fornecem boas previs oes dos dados experimentais, sendo a previsao do primeiro modelo melhor para o conjunto das duas frequencias |
| Disciplines: | Geociencias |
| Keyword: | Mineralogía, petrología y geoquímica, Granulometría, Minerales pesados, Contenido de agua, Arena |
| Keyword: | Earth sciences, Mineralogy, petrology and geochemistry, Granulometry, Heavy minerals, Water content, Sand |
| Full text: | Texto completo (Ver PDF) |
